The present invention relates to a mold tool for forming an electronic component having a semiconductor chip sealed on a substrate by resin, a method for forming the electronic component, and a lead frame on which a semiconductor chip can be put and thereafter the chip on the frame is sealed by resin.
Referring to FIGS. 6-8, a known semiconductor sealing method will be described hereinafter. FIG. 6 is a schematic cross-sectional view of a known resin-molded electronic component 21 and FIGS. 7 and 8 show example phenomena caused by molding in the known semiconductor sealing method.
In FIG. 6, a substrate 23 for attaching a semiconductor 22 is flat. The chip 22 is sealed on the substrate 23 by resin, resulting in a difference between the distance (c) from the upper surface of the chip 22 to the upper surface of a sealing portion 27 and the distance (d) from the lower surface of the substrate 23 to the lower surface of the sealing portion 27.
However, since the configuration elements such as the sectional area and the thickness of the molded product have a great effect on the flow of the molten resin, the above construction causes the resin to firstly flow in the lower mold having a cavity with a larger depth than the depth of the upper mold as shown in FIG. 7 and then flow to the upper mold after the lower cavity of the lower mold is filled with resin. As a result thereof, the resin flow forces gas in the cavities to be held in the upper mold having the cavity with the smaller depth, forming voids in the upper cavity, thus causing disadvantages such as poor insulation properties of the product. As shown in FIG. 8, if the substrate 23 is easily deformed, the substrate 23 is easily deformed by the resin flow. The forward ends 28a and 28b of the two resin flows entering the upper and lower cavities after passing through a gate 24 are difficult to coincide with each other. Therefore, after the lower cavity is filled with the resin, the pressure caused in the lower cavity by the resin is applied to the substrate 23 to deform, resulting in a poor quality of the electronic component molded by resin.